Snowmobile suspension and drive train

ABSTRACT

A snowmobile suspension and drive train for supporting a snowmobile chassis and guiding an endless loop type track, the snowmobile suspension and drive train comprises an endless loop type snowmobile track supported by a suspension mechanism; wherein the track is being driven and guided at a rear track position with track drive sprockets and is supported and guided at a front track position with front idler wheels, and wherein an upper portion of the track is guided and supported at an intermediate position over top track wheels. The snowmobile suspension wherein the suspension mechanism includes a diagonally extending upper frame pivotally connected at a pivot point to a horizontally oriented lower frame in scissor relationship such that the suspension can move between a raised position and a lowered position.

The present invention is a continuation in part and claims priority frompreviously filed US regular application filed on Aug. 22, 2008application Ser. No. 12/230,045 inventor Shawn Watling under the title;Snowmobile Suspension and Drive Train. The present invention relates toa snowmobile suspension and drive train.

FIELD OF THE INVENTION BACKGROUND OF THE INVENTION

Traditional snowmobile drive trains use a forward drive axle which isdriven by a jack shaft which obtains power from the secondary clutch.The present invention eliminates the forward drive axle and instead usesa rear drive which includes a chain and sprocket drive.

SUMMARY OF THE INVENTION

A snowmobile suspension and drive train for supporting a snowmobilechassis and guiding an endless loop type track, the snowmobilesuspension and drive train comprising an endless loop type snowmobiletrack supported by a suspension; wherein the track is being driven andguided at a rear track position with track rear drive sprockets and issupported and guided at a front track position with front idler wheels,wherein an upper portion of the track is guided and supported at anintermediate position over top track wheels.

Preferably wherein the front idler wheels positioned within 6 incheseither side of the balance point.

Preferably wherein the front idler wheels positioned within 2 incheseither side of the balance point.

Preferably wherein the front idler wheels positioned at the balancepoint.

Preferably wherein the suspension includes a upper frame pivotallyconnected at a pivot point to a horizontally oriented lower frame inscissor relationship such that the suspension movable between a raisedposition and a lowered position.

Preferably wherein in the lowered position the upper frame is orientedsubstantially parallel to the lower frame.

Preferably wherein in the raised position the upper frame is orientedsuch that it extends diagonally upwardly relative to the lower frame.

Preferably wherein in the raised position a reaction force vectorpassing Through the pivot point and parallel to the frame rail willintersect with the center of gravity.

Preferably wherein in the raised position a reaction force vectorpassing through the pivot point and parallel to the frame rail will passabove the center of gravity.

Preferably 5 wherein the pivot point dividing upper frame into a reararm portion on one side of the pivot point and a front arm portion onthe other side of the pivot point.

Preferably wherein in the lowered position rear arm portion raises thedrive sprockets off of the ground creating a track lifted portion beingthe part of the track no longer contacting the ground thereby creating atrack short contact length being the portion contacting the ground.

Preferably wherein in the raised position rear arm portion lowers reardrive sprockets toward the ground eliminating a track lifted portionthereby creating a track long contact length being the portioncontacting the ground.

Preferably wherein the lower fame including left and right frame membershaving mounted thereon track wheels for supporting the track rollablythereon.

Preferably wherein the pivot point is spaced upwardly from the framemembers and located in pivot flange projecting upwardly from a rear endof each frame member thereby creating L shaped left and right framemembers.

Preferably wherein the suspension is fastened to the chassis with frontadjustable shocks and rear adjustable shocks such that the front trackportion and the rear track portion can be adjusted up and downindependently of each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only withreference to the following drawings in which:

FIG. 1 is a side schematic partial cut away view of the presentinvention a snowmobile suspension and drive train.

FIG. 2 is a top plan view of the snowmobile suspension and drive train.

FIG. 3 is a side elevational view of the snowmobile suspension and drivetrain.

FIG. 4 is a schematic partial assembly view of a portion of the rearshock assembly and adjusting mechanism.

FIG. 5 is a schematic partial cut away view of the rear shock assembly.

FIG. 6 is a top schematic partial cut away view of the snowmobilesuspension and drive train.

FIG. 7 is a partial schematic cut away side plan view of the snowmobilesuspension and drive train.

FIG. 8 is a schematic partial view of components of the chain tensioningassembly.

FIG. 9 is a schematic assembly of a portion of the front shock assembly.

FIG. 10 is an assembled partial schematic perspective view of the frontshock assembly together with the slide rails.

FIG. 11 is a top plan schematic view of the rear shock assembly and thefront shock assembly shown mounted on the ladder bar frame.

FIG. 12 is a partial side schematic view of the rack and rear idlewheels together with the rear shock assembly shown in a first positionin dark lines and a second position in light dashed lines and in a thirdposition an even lighter dashed lines.

FIG. 13 is a top schematic plan view of a portion of the snowmobilesuspension and drive train together with the engine and primary andsecondary clutch.

FIG. 14 is a schematic partial cut away view of the driven jack shafttogether with various component mounted thereon including the brakerotor, the front idler wheels, the front drive split sprocket and thesecondary clutch.

FIG. 15 is an exploded assembly view of the mounting hub, the frontdrive split sprocket and the pins and bolts for assembly of thecomponents.

FIG. 16 is a rear perspective assembled schematic view of an alternateembodiment of a snowmobile suspension and drive train.

FIG. 17 is a top plan view of the snowmobile suspension and drive trainshown in FIG. 16.

FIG. 18 is a schematic side elevational view of the snowmobilesuspension and drive train shown in solid lines together with asnowmobile chassis shown in dashed lines.

FIG. 19 is an enlarged side elevational schematic view of the snowmobilesuspension and drive train shown in FIG. 18.

FIG. 20 is a schematic side elevational view of the snowmobilesuspension and drive train deployed in a chassis of a snowmobile shownin dashed lines.

FIG. 21 is a side elevational schematic side view of the snowmobilesuspension and drive train shown in FIG. 16 in the raised position.

FIG. 22 is a schematic side elevational plan view of the snowmobilesuspension and drive train in solid lines deployed onto a snowmobilechassis shown in dashed lines.

FIG. 23 is an expanded side elevational schematic view of the snowmobilesuspension and drive train together with front and rear adjustableshocks.

FIG. 24 is a side elevational schematic view of the snowmobilesuspension and drive train shown in FIG. 16 together with the drive beltand pulleys together shown deployed onto a chassis of a snowmobile.

FIG. 25 is a top schematic plan view of the snowmobile suspension anddrive train shown in FIG. 16 using a cog belt drive system to drive therear drive sprockets rather than a chain.

FIG. 26 is a top schematic plan view of the snowmobile suspensionshowing the engine drive line mounted on the other side of thesuspension and drive train relative to FIGS. 25 and 17.

FIG. 27 is a side elevational schematic side view of an alternatearrangement of the snowmobile suspension and drive train in the raisedposition depicting an inclined approach.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The attached figures show a snowmobile suspension and drive train whichincludes the following major components, namely ladder bar frame 202,front shock assembly 204, rear shock assembly 206, drive chain 250, reardrive assembly 210, front drive assembly 212, engine 214, primary clutch216 and driven secondary clutch 218.

Referring now to FIGS. 13, 14 and 15 front drive assembly 212 includes alive driven jack shaft 220, a front drive split sprocket 222, a mountinghub 224 and idler wheels 226.

Front drive split sprocket 222 is mounted onto mounting hub 224 usingpins 230 and bolts 232. Mounting hub 224 is mounted onto driven jackshaft 220 in traditional manners including splines etc., for rigidlymounting, mounting hub 224 onto driven shaft 220.

Driven shaft 220 also includes brake rotor 236 and brake calliper 238mounted on one end of the driven shaft 220 and the secondary clutch 218mounted on the other end of driven shaft 220.

Engine 214 drives primary clutch 216 which in turn drives secondaryclutch 218 via drive belt 240.

Front drive split sprocket 222 drives drive chain 250.

Referring now to FIGS. 2, 3, 4 and 5, rear drive assembly 210 includesfixed rear axle 302, track sprockets 304, driven chain sprocket 306,rear idler wheels 308, track tension assembly 310, rear shock assembly206 and chain tensioning assembly 312.

Rear shock assembly 206 includes coil over rear shock 402, upper pivotarm 404, lower pivot arm 406, rear pivot shaft 408, sprag or splinedfaces 410 and connecting link 412.

Ladder bar frame 202 includes outer rails 602, cross member 608,stiffening member 610, and has attached thereto idler track wheels 604and slide rails 606.

Front shock assembly 204 best shown in FIGS. 9, 10 and 11, includes anadjustable coil over shock 702, a front pivot arm 704, a slide railconnecting link 706, aperture for pivot arm shaft 708, connecting pins710, connecting link shaft 712 and pivot arm shaft 714. Front pivot arm704 also includes shock flanges 720, and shock mounting holes 722.

Chain tension assembly 312 includes the drive chain 250, a slottedadjustment bracket 802 and a chain idler wheel 804.

Ladder bar frame 202 is connected to the snowmobile chassis at frontladder bar pivot shaft 692.

Referring now to FIG. 12 showing rear shock assembly 206 together withthe track in various positions by adjusting the rear shock assembly 206namely by setting the spline faces 410 relative to each other byclamping upper pivot arm against rear pivot shaft 408. In this mannerone can align upper pivot arm 404 at relative angles to lower pivot arm406. So for example, one can obtain a track first position 902 byengaging sprag or spline faces 410 in such a manner that lower pivot armtakes on first position 912. One can obtain track second position 904 byadjusting lower pivot arm into second position 914 and one can obtain atrack third position 906 as shown in FIG. 12. Therefore, the track 950can be adjusted to various heights relative to the chassis of thesnowmobile by adjusting the sprag or spline faces 410 of the rear pivotshaft 408 relative to the upper pivot arm 404 with bolt 405. In thismanner, one can adjust the ride height to suit individual ridingconditions and increase or decrease the suspension travel.

Snowmobile Drive Train In Use

The presently described rive train includes an engine 214 which drives aprimary clutch 216 which is connected to a secondary clutch 218 via adrive belt 240. Secondary clutch 218 drives a driven jack shaft 220which is a live shaft which includes front drive split sprocket 222mounted onto a mounting hub 224 connected to driven jack shaft 220.Driven jack shaft 220 also includes a brake rotor 236 and a brakecalliper 238 mounted on one distal end thereof. In addition, there aretwo front idler wheels 226 which guide track 950 over top of and aroundfront drive assembly 212. Front drive split sprocket 222 drives a drivechain 250 which in turn is connected to driven chain sprocket 306 whichis mounted on fixed rear axle 302.

Fixed rear axle 302 includes two sets of track sprockets 304 which aremounted on either side of driven chain sprocket 306. In addition, rearidler wheels 308 guide track 950 around rear drive assembly 210. Drivechain 250 in addition passes overtop of two chain idler wheels 804, thefirst positioned closer to the front of the snowmobile and the secondchain idler wheel 804 is part of a chain tensioning assembly 312. Chaintensioning assembly 312 includes a slotted adjustment bracket 802 alongwhich chain idler wheel 804 can be mounted at various positions in orderto adjust chain tension. A chain guard 290 is also mounted on the upperpart of the drive assembly to ensure that chain 250 does not makecontact with any of the parts of the ladder bar frame 202. This drivesystem results in reduced moving components and increased flexibility inthat any number of the sprocket combinations can be used to determinethe final drive ratio and to optimize the drive train for any particulardriving condition. In addition, rather than the front portion of thetrack being driven, in this case the rear portion of the track isdriven, resulting in completely different driving characteristics of thesnowmobile due to the tensioning on track 950 and the torque imposedupon the snowmobile during hard acceleration.

This drive setup allows for a very stiff ladder bar frame constructionhaving cross member 608 and stiffening member 610 which pivot about onepoint near the front of the snowmobile namely, about front ladder barpivot shaft 692.

Snowmobile Suspension In Use

The snowmobile suspension includes a front shock assembly 204 and tworear shock assemblies 206. Front shock assembly 204 includes anadjustable coil over shock 702 which is attached at one end to ladderbar frame 202 and at the other end to shock mounting hole 722 in frontpivot arm 704. In turn, slide rail connecting link 706 is hinge ablyconnected to front pivot arm 704 with a connecting pin 710. Slide railconnecting link 706 is attached to slide rail 606 which a connectinglink shaft 712. Slide rail 606 is very much the same as the slide railassemblies found on existing snowmobiles having a number of idler trackwheels 604 for guiding the track along the bottom of the snowmobile.Rear shock assembly 206 includes rear pivot shaft 408. On each distalend of rear pivot shaft 408, a coil over rear shock 402 is mounted to anupper pivot arm 404 which is connected to rear pivot shaft 408 with asprag or spline faces 410 found on both the upper pivot arm 404 and therear pivot shaft 408. The spline faces are meshed together using a bolt405 for rigidly connecting upper pivot arm 404 to rear pivot shaft 408.In addition, there is a lower pivot arm 406 rigidly attached to rearpivot shaft 408 which in turn is connected to a connecting link 412which is connected at one to the ladder bar frame 202 and at the otherend to lower pivot arm 406. As best shown in FIG. 12 via adjusting theposition of the sprag or spline faces 410, one can select any number ofangular positions of lower pivot arm 406 in relationship to upper pivotarm 404. FIG. 12 shows three such possibilities namely track firstposition 902, track second position 904 and track third position 906. Byadjusting the angular relationship between the upper pivot arm 404 andthe lower pivot arm 406 using the sprag or spline faces 410, one canhave a high riding position and or a low riding position and/or selectlarge suspension travel or smaller suspension travel depending upon theposition of the pivot arms.

The suspension will also include a track tension assembly 310 which isan assembly well known in the present art. In order to adjust thetension on track 950, first of all the chain tensioning assembly 312would be backed off completely in order to remove any tension on drivechain 250. Once drive chain 250 is slack, one can then adjust the tracktensioning assembly 310 in order to obtain the necessary tension ontrack 950. Thereafter, the chain tensioning assembly 312 would beadjusted to obtain the necessary tension on drive chain 250.

Description of Alternate Embodiment of a Snowmobile Suspension and DriveTrain

An alternate embodiment of a snowmobile suspension and drive train isshown generally as 1000 in FIG. 16 and following:

Snowmobile suspension and drive train 1000 includes the following majorcomponents namely, upper frame 1002 pivotally attached and connected tolower frame 1004 at a pivot point 1007 with a pivot shaft 1006. Thetrack 1102 is an endless loop type snowmobile track supported by thesuspension wherein track 1102 is being driven and guided at a rear trackposition 1404 with track drive sprockets 1036 and is supported andguided at a front track position 1402 with front idler wheels 1052 andthe upper portion 1406 of track 1102 is guided at an intermediateposition 1408 overtop track wheels 1026. Note that track 1102 is drivenat the rear track position 1404 which is where the track just breakscontact with ground 1101. With suspension 1000 in raised position 1008track 1102 breaks contact with the ground under track drive sprockets.With suspension 1000 in lowered position 1010 track 1102 breaks contactwith the ground under the rear most track wheel 1044. Track 1102 justbegins to make contact with ground 1102 at front track position 1402under front idler wheel 1052. Upper portion 1406 of track 1102 does notmake contact with ground 1101.

The suspension includes a diagonally extending upper frame 1002pivotally connected to a horizontally oriented lower frame 1004 inscissor relationship pivoting at pivot point 1007. Upper frame 1002 canbe pivoted in scissor like fashion relative to lower frame 1004 betweena raised position 1008 shown in FIG. 21 and a lowered position 1010shown in FIG. 19. In the lowered position the upper frame 1002 isoriented substantially parallel to the lower frame 1004 meaning theframes are within plus or minus 10 degrees being the angle subtended bythe two frames. In the raised position the upper frame is oriented suchthat it extends diagonally upwardly relative to the pivot point as shownin FIG. 21.

Upper frame 1002 is preferably designed and fabricated in the style of aladder bar 1012 having a right frame rail 1014 and a left frame rail1016 connected together with bars.

Upper frame 1002 also includes the following components namely, frontdriven shaft 1018 having attached thereon a brake system 1020, a motordriven pulley 1022 receiving power from the motor via a motor drive belt1074. Front driven shaft 1018 further includes front sprocket 1024 andtop track wheels 1026. Front driven shaft 1018 is located at the top end1028 of upper frame 1002 and rear drive shaft 1030 is located at bottomend 1032 of upper frame 1002. Rear drive shaft 1030 has mounted thereonrear drive sprocket 1034 for receiving a chain thereon and track drivesprockets 136 which transmit power to the snowmobile track 1102.

Lower frame 1004 includes a right frame member 1040, a left frame member1042, and track wheels 1044.

Each of the frame members has an idler end 1046 and a rear end 1048. Atidler end 1046, idler shaft 1050 is mounted having front idler wheels1052 mounted thereon. Front idler wheels guide the track 1102 around thesnowmobile suspension and drive train 1000.

Lower frame 1004 at rear end 1048 includes a pivot flange 1054 which asshown in the Figures is an L-shaped flange generally extendingperpendicular to the frame members 1042 and 1040. Proximate a top end1056 of pivot flange 1054 is mounted pivot shaft 1006 there throughthereby pivotally connecting upper frame 1002 to lower frame 1004 atpivot point 1007.

Included at the idler end 1046 is a track tensioning mechanism 1060 forobtaining the necessary track tension onto the track and also forfacilitating removal and mounting of the track 1102 onto the snowmobilesuspension and drive train components 1000.

Referring now to FIG. 17, the snowmobile suspension and drive train 1000is shown schematically in a top plan view together with the motor 1070which drives a motor drive pulley 1072 which in turn drives a motordrive belt 1074 which in turn drives the motor driven pulley 1022 whichin turn drives the front driven shaft 1018.

Brake system 1020 typically includes a brake rotor 1076 and a brakecalliper 1078 of the type known in the art.

Front sprocket 1024 drives a chain 1080 which in turn transmits powerback to the rear sprocket drive 1034 which in turn rotates rear driveshaft 1030 which in turn rotates drive track sprockets 1036 whichtransmit turning power to the track 1102 not shown in this Figure.

Referring now to FIGS. 18 and 19 snowmobile suspension and drive train1000 in FIG. 19 is shown in the lowered position 1010 together with atrack 1102 mounted thereon.

In the lowered position 1010 shown in FIGS. 18 and 19, top end 1028 ofupper frame 1002 is lowered downwardly to the point where upper frame1002 lies parallel and adjacent to lower frame 1004. In this positionthe bottom end 1032 is raised off of the ground 1101, thereby reducingthe total contact length of the track 1102 as shown in FIGS. 18 and 19.

In particular, shown in FIG. 18 is the contact portions of track 1102when the snowmobile suspension and drive train 1000 is in the loweredposition 1010.

Track 1102 has a short contact length shown as S1110 when in the loweredposition 1110 and also has a track lifted portion denoted as C1112thereby reducing the total contact surface of track 1102 onto the ground1101. The advantages of having a short contact length as denoted as 1110will be discussed below.

Also will be noted in FIGS. 18 and 19 that the balance point of theentire snowmobile with no passengers aboard lies at approximately theposition shown as BP namely 1114 which is known in the art as thebalance point and the center of gravity lies at a point shown as CG1301. The center of the front idler wheels 1052 are positioned within 6inches either side of the balance point, and preferably within 2 inchesof either side of the balance point, and preferably at the balance pointmeaning that some portion of front idler wheel lies over top of balancepoint BP 1114 of the sled.

Additionally shown in FIG. 19 is right frame rail 1014 of upper frame1002. Right frame rail 1014 can be subdivided into the rear arm portionshown as A and denoted as 1120 and the front arm portion shown as B anddenoted as 1122. Upper frame 1002 pivots about pivot shaft 1006 whichsubdivides right frame rail 1014 into the rear arm portion A1120 and thefront arm portion B1122.

The reader will note that when the top end 1028 of right frame rail 1014is raised thereby raising front arm portion 1122, the bottom end 1032 ofright frame 1014 is lowered thereby lowering rear arm portion A1120.

Referring now to FIGS. 20 and 21, the snowmobile suspension and drivetrain shown generally as 1000 is shown in the raised position 1008. Inthe raised position, the total contact length is long contact length Ldenoted 1130 in FIG. 20 and the reader will note that the track liftportion denoted as C1112 now makes contact with the ground 1101. In theraised position 1008, the track area contacting the ground is maximizeddue to the extended long contact length L1130 achieved by loweringbottom end 1032 of upper frame 1002. The snowmobile chassis 1050 isshown in dashed lines in FIGS. 18 and 20 for illustrative purposes onlyto show schematically how the snowmobile suspension and drive train 1000would be deployed relative to a chassis 1050.

Referring now to FIGS. 22 and 23, snowmobile suspension and drive train1000 is shown deployed onto a snowmobile chassis 1050 shown in dashedlines. The diagram show front adjustable shocks 1200 and rear adjustableshocks 1202 which are connected to chassis 1050 and are of the typewhich can be raised and lowered. Therefore, one can select to lower thefront adjustable shocks 1200 and/or the rear adjustable shocks 1202and/or both thereby adjusting the ride, quality, height and as wellaffecting the total track contact length shown as L1130 and S1110 inFIGS. 18 and 20.

FIG. 25 is a top schematic plan view of the snowmobile suspension anddrive train 1000 similar to the view shown in FIG. 17, however in thecase of FIG. 25 the chain 1080 is replaced with a cog belt 1220 and aperson skilled in the art will note that rear sprocket drive 1034 andfront sprocket 1024 would be exchanged with front cog 1222 and rear cog1224 in order to transmit the drive forces from cog belt 1220 to therear cog 1224. In all other respects, the snowmobile suspension anddrive train 1000 shown in FIG. 25 is similar to the snowmobilesuspension and drive train 1000 shown in FIG. 17.

Referring now to FIG. 26, the reader will note that the snowmobilesuspension and drive train shown generally as 1000 may have differentlyarranged drive trains. For example in FIG. 26 motor 1070, motor drivepulley 1072, motor drive belt 1074 and motor driven pulley 1022 areoriented on the left side rather than on the right side shown in FIGS.17 and 25. It may be possible that the motor position may be found to bemore convenient and/or efficient in another position than as shown ineither FIG. 25 or 26 and this would still be part of the scope of thespirit of this snowmobile suspension and drive train.

In addition in FIG. 26 is shown sponsons 1304 which essentially is asnow floatation device mounted longitudinally along both sides of framerails 1014 and 1016. Sponsons 1304 are used to add floatation in deepsnow like a ski and help prevent the chances of getting stuck. The shapeand size of the sponsons is optimized for different applications such ascarving in deep snow, in which case one would want the sponsons to actlike a ski or rudder. The sponsons may also be constructed larger toform a shroud in front of the track radius at the rear track position1404 to prevent inside radius of the track from grabbing or hooking thesnow up into the air as the snow enters inside of the track whiletravelling around the rear drive sprocket 1034 or rear idler wheels.This entrainment of snow may cause a certain amount of drag in deep snowand the sponsons 1034 can be shaped to reduce this drag. The sponsonwill also add protection to other suspension components and absorbimpact during possible collision with objects.

Referring now to FIGS. 18 and 20, one will note that these figures alsodepict the center gravity 1301 as shown in the diagrams. The position ofthe center of gravity of the snowmobile relative to the orientation ofthe ladder bar frame 1012 will create certain reaction forces when underheavy acceleration and deceleration. It is preferable that the ladderbar frames 1012 instance center is pointing at or above the center ofgravity 1301 in order to produce the optimal reaction forces.

Use of Snowmobile and Suspension Drive Train 1000

Reaction force is applied to ladder bar frame 1012 by means of torqueapplied via a chain 1080 and/or a cog belt 1220 to the rear drivesprocket 1034 or rear cog 1224. This creates a reaction force vectoralong the instant center of the ladder bar frame 1012. In the raisedposition for example a force vector runs along an imaginary line knownas the instant center which passes through the pivot point 1007 andparallel to the frame rails 1014, 1016. This reaction force vectorpreferably passes above or intersects with the center of gravity 1301when the suspension is in the raised position 1008. This reaction forcevector dictates the behavior of the chassis movement relative to thecenter of gravity 1301. Torque applied at the rear drive shaft 1030attempts to extend the suspension while weight transfer attempts tocompress the suspension. Under operating conditions, the balance ofthese forces is created and the resulting forces increase pressure tothe ground while having minimal affect on the front suspension (thepressure on the skis). Force vectoring is variable by controlling reardrive shaft 1030 torque and the position of the ladder bar frames 1012instant center relative to the vehicle center of gravity 1301. Foroptimal performance one would like to have the ability to position thereaction force vector to pass above or intersect with the center ofgravity 1301.

A conventional suspension and drive behaves in an opposite manner whichis a disadvantage. Under heavy acceleration in a conventionalsuspension, the front suspension is unloaded and therefore, the skipressure on the front skis decreases, making it more difficult tocontrol the steering of the snowmobile. While carrying a passenger,these disadvantages of the conventional suspension become even moreapparent.

By adjusting the height of rear adjustable shocks 1202 and frontadjustable shocks 1200, one is able to independently adjust the frontand/or rear height of snowmobile suspension drive train 1000. In FIG. 19for example, the suspension is shown in the lowered position 1010,wherein the contact length of the track is at short contact length 1110.In FIG. 21 for example the snowmobile suspension and drive train 1000 isshown in the raised position 1008, wherein the contact of the track 1102is the long contact length L shown as 1130. The length of the track 1102contacting any surface such as ground 1101 is variable and can beextended and/or compressed depending upon whether the suspension is inthe lowered position 1010 and/or the raised position 1008. In deep snowfor example, increased surface area of the track 1102 is desired andtherefore the suspension is put into the raised position 1008 whichmaximizes the contact length L 1130 and also raises the center ofgravity of the snowmobile. This position is preferably for aggressiveriding in deep snow and/or over rough terrain.

By adjusting the suspension to a lower ride height namely, putting in tolowered position 1010, one will improve the handling of the snowmobileby decreasing the surface area of track 1102 to the short contact lengthas 1110 and also lowering the center of gravity 1301. This permitstighter turning, reduces lateral weight transfer due to the lowering ofcenter of gravity 1301 and improves turning capabilities and stabilityof the snowmobile. Therefore, suspension right height adjusts trackgeometry to compliment the intended purpose of the riding conditions.

Snowmobile suspension and drive train 1000 is essentially an endlessloop track 1102 consisting of front idler wheels 1052 placed at thefront track position 1402. The idler wheels are located directly belowthe snowmobile center of gravity 1301 and at the balance point 1114 ofthe snowmobile.

As indicated above by placing the suspension in lowered position 1110,one can reduce the track 1102 contact length and by raising thesuspension into the raised position 1008, one can increase the trackcontact namely into long contact length L 1130.

The mechanical geometry of snowmobile suspension and drive train 1000provides better performance under deceleration of the snowmobile. Theinability of conventional snowmobiles to reduce speed and come to acomplete stop is well known. Several factors are part of thisundesirable behavior. The approach angle of a traditional snowmobile atthe very first contact point of the track to the snow creates a rampeffect while braking. Snow accumulation in front of the track iscompressed and forced to travel below the track. This causes ahydroplane type action, thereby reducing the ability of snowmobile tocome to a fast halt.

Secondly, the track tension in a conventional drive created by the driveaxle attempts to straighten and compress the suspension at the front ofthe track under deceleration conditions further inducing the ramp effectand further increasing the hydroplaning effect.

Thirdly, the initial contact of the track is almost 14 further back ofthe center of gravity 1301 as compared to the present snowmobilesuspension and drive train 1000. A lower percentage of the total vehicleweight is applied to the track and is further amplified when weight istransferred forward during hard breaking onto the skis.

The present snowmobile suspension and drive train 1000, dramaticallyimproves the ability to reduce speed, increase control and come to afast stop. The following factors make this possible. The front idlerwheels 1052 found in the forward portion of the track are almostdirectly under the vehicles center of gravity 1301 and directly underthe snow machines balance point 1114. The center of gravity point 1301of course changes depending upon the number of passengers that areriding on the snowmobile, but generally speaking, the center of gravity1301 will move further back as additional passengers are added to thevehicle. This movement on the center of gravity position 1301 backwardwith the additional passengers, aids braking since a high percentage ofthe vehicles weight is applied to the front idler wheel 1052 under highbreaking.

A third factor to increase traction under heavy breaking involves adirection of the forces applied to the front idler wheel 1052. The toptrack wheel 1026 applies force forwardly through the right and leftframe members 1040 and 1042. Thereby transferring the energy andpivoting the ladder bar frame 1012. This effect causes further force tobe applied to front idler wheel 1052 thereby reducing or preventinghydroplaning and causing idler wheel 1052 to dig in or assert morepressure onto ground 101. The front skis therefore remain firmly plantedin the snow therefore maintaining steering control of vehicle anddeceleration is greatly improved.

In addition, the distance between the motor drive pulley 1072 and themotor driven pulley 1022 is increased. This provides greater efficiencyof the variable speed transmission since the area of contact around theprimary clutch 1021 is increased, therefore reducing belt slippage,lowering heat created, increases belt life, increases reliability andeffectively transfers power more efficiently to front driven shaft 1018.Manufacturing costs and assembly time are also reduced, due to lesscritical specifications for drive belt alignment due to the long drivecenter between the motor drive pulley 1072 and the motor driven pulley1022. In addition, the chain case which is typically a part of thepresent day snowmobile drive trains is completely eliminated andtherefore, less distance is required to transmit power to the ground.

The track tension is applied to approximately 40% of the track totransmit power to only the portion that contacts the ground, as the topside of the track essentially free wheels. This is because the reardrive shaft 1030 is the driven axle of the drive train. By applying therotating or the torque to the rear portion of the track, one isessentially pulling track 1102 around front idler wheel 1052 andbackwards around rear drive sprocket 1034, therefore applying tensionalong the bottom portion of track 1102 which is more or less in contactwith the ground 101. This reduces track fatigue and proves rollingresistance around the large diameter front idler wheel 1052. The trackcan be operated quite loose with very little tension and without trackskipping or ratcheting whether breaking or accelerating.

A convention sled applies tension to 90% of the track in order totransmit power to the ground. A conventional sled a large portion of thetrack is part of the transmission and in particular the top side of thetrack transmits power to the ground.

The reader will note that the front and rear track suspension can travelindependently. In other words, front adjustable shock 1200 and rearadjustable shock 1202 can be independently raised and lowered and notcoupled together as in a conventional suspension system. The presentsuspension can isolate the tuning, front or back and give considerableincrease in rider comfort and control. In conventional suspensions, byadjusting either the front or back, it automatically affects other partsof the suspension.

The present invention applies chassis load through the through theladder bar frame 1012 to the rear drive shaft 1030. Therefore, when apassenger is present on a snowmobile, they are sitting well ahead of therear drive shaft 1030. The passenger's weight does proportionally addweight to the front skis which is need to maintain control of thesnowmobile.

This is not the case in conventional snowmobiles, wherein the front skisare unloaded with the presence of passengers onto the back of thesnowmobile.

The present design is very versatile in that the user has the capabilityto adjust ride height while stationary or under motion. It is possibleto have the entire weight of the vehicle placed on the front idlerwheels 1052 which allows the operator to easily pivot the snowmobilearound balancing only on the front idler wheel 1052. A 500 pound sledunder these conditions requires only 20 pounds of pull at a rear grabhandle located near the rear drive sprocket 1034 in order to turn thesled totally around on dry pavement, or hard packed snow by positioningthe entire weight of the snowmobile over front idler wheel 1052. Smallchildren and the elderly with back trouble and people who are unable tobend and push and/or pull to a great degree can easily completely pivotthe snowmobile around the front idler wheels 1052 by simply positioningthe suspension in such a manner that the majority of weight isconcentrated over the front idler wheel 1052.

The same capability while riding the vehicle, allows the operator toraise the skis off the ground to cross the road or surface that maycause damage to the front ski carbide runners and also to publicproperty.

The same capability also gives the operator the choice to adjust the skipressure downwards while operating the snowmobile. This is desirable fordifferent operating conditions which change the handling characteristicsand the bands of the snowmobile. For instance if you are carrying aheavy load or a passenger, you may choose to raise the rear end in orderto level out the vehicle. In deep snow you may choose to have little orno ski pressure to make the snowmobile nibble and easy to carve by onlyshifting your weight.

In addition to this the present design reduces manufacturing costs,assembly time, it simplifies and reduces the number of parts. The methodused to manufacture may be less costly and in particular maintenanceprocedures may also be less time consuming.

Referring now to FIG. 27 which shows an alternate suspension set up withan inclined approach 2006 proximate front track portion 2012. Lowerframe 1004 includes an upwardly curved forward end 2010 thereby creatingan inclined approach 2006 to track 1102. The short contact length 2004and the long contact length 2002 are modified respectively relative theprevious embodiment due to the inclined approach 2006 as depicted inFIG. 27.

It should be apparent to persons skilled in the arts that variousmodifications and adaptation of this structure described above arepossible without departure from the spirit of the invention the scope ofwhich defined in the appended claim.

1. A snowmobile suspension for supporting a snowmobile chassis and forguiding and supporting an endless loop type track, the snowmobilesuspension comprising: a) an endless loop type snowmobile tracksupported by a suspension; b) the suspension including a frame housedwithin the endless loop track, c) the suspension further including aguide means for guiding the track around the suspension; d) wherein theframe includes an upper frame pivotally connected at a pivot point to ahorizontally oriented lower frame housed within the endless loop trackin scissor relationship, such that the suspension movable between araised position and a lowered position.
 2. The snowmobile suspensionclaimed in claim 1 wherein the guide means including front idler wheelsoperably mounted to the lower frame at a front track position.
 3. Thesnowmobile suspension claimed in claim 2 wherein the lower frameoriented such that at the front track position the track begins to makecontact with the ground under the front idler wheels.
 4. The snowmobilesuspension claimed in claim 2 wherein the lower frame including anupwardly curved forward end such that at the front track portion thetrack is at an inclined approach relative to the ground.
 5. Thesnowmobile suspension claimed in claim 1 wherein the guide meansincluding top track wheels mounted at a top end of the upper frame andtrack drive sprockets mounted at a bottom end of the upper frame forguiding the track around the suspension.
 6. The snowmobile suspensionclaimed in claim 5 wherein the top track wheels located at the trackintermediate position for guiding a track upper portion around thesuspension.
 7. The snowmobile suspension claimed in claim 1, wherein inthe lowered position the upper frame is oriented substantially parallelto the lower frame such that a track lifted off portion is lifted offthe ground at the rear track position.
 8. The snowmobile suspensionclaimed in claim 1 wherein in the raised position the upper frame isoriented such that it extends diagonally relative to the lower frame,such that at the rear track position the track breaks contact with theground under the track drive sprockets.
 9. The snowmobile suspensionclaimed in claim 1 wherein the lower frame connected at a pivot point ata rear end of the lower frame and including front idlers wheels mountedat an idler end of the lower frame.
 10. The snowmobile suspensionclaimed in claim 1 wherein the pivot point dividing the upper frame intoa rear arm portion on one side of the pivot point and a front armportion on the other side of the pivot point.
 11. The snowmobilesuspension and drive train claimed in claim 10 wherein in the raisedposition the rear arm portion urging the track drive sprockets and thetrack there beneath onto the ground such that a track long contactlength being the portion contacting the ground.
 12. The snowmobilesuspension claimed in claim 10 wherein in the lowered position the reararm portion urging the track drive sprockets and the track there beneathoff of the ground resulting in a track short contact length being theportion contacting the ground.
 13. The snowmobile suspension claimed inclaim 1 wherein in the raised position a reaction force vectorintersecting the pivot point and parallel to the upper frame willintersect with the center of gravity.
 14. The snowmobile suspensionclaimed in claim 1 wherein in the raised position a reaction forcevector passing through the pivot point and parallel to the upper framewill pass above the center of gravity.
 15. The snowmobile suspensionclaimed in claim 1 wherein the lower frame including left and rightframe members having mounted thereon track wheels for supporting thetrack rollably thereon.
 16. The snowmobile suspension claimed in claim15 wherein the frame members including a pivot flange projectingupwardly from a rear end of each frame member forming L shaped left andright frame members such that the pivot point is located on the pivotflange.
 17. The snowmobile suspension claimed in claim 1 wherein theframe is suspended to the chassis with a front biasing means and a rearbiasing means such that the track at the front track position and thetrack at the rear track position can be adjusted up and downindependently of each other.
 18. The snowmobile suspension claimed inclaim 17 wherein the front biasing means includes front adjustableshocks and the rear biasing means includes rear adjustable shocks. 19.The snowmobile suspension claimed in claim 1 wherein the frame isfastened to the chassis with two front adjustable shocks to the idlerend of the lower frame and two rear adjustable shocks at the bottom endof upper frame such that the track at the front track position and thetrack at the rear track position can be adjusted up and down relative toa chassis and independently of each other.